Commercial ammonia synthesis plants

The chapter by Bridger and Woodward deals with methanation as a means for removing carbon oxides from ammonia synthesis gas. This technology, together with earlier pioneer work by Dent and co-workers (I), are the forerunners of all modern methanation developments. The chapter deals with catalyst formulation and characterization and with the performance of these catalysts in commercial plants as a function of time on-stream. 

Comparable to IGT technology for syngas generation is the high-temperature Winkler (HTW) gasification process. A commercial HTW unit was installed in 1988 at a Finnish ammonia synthesis plant and has operated successfully using peat as a feedstock.51... 

Koppers-Totzek A coal gasification process using an entrained bed. The coal is finely ground and injected in a jet of steam and oxygen into a circular vessel maintained at 1,500°C. Reaction is complete within one second. The ash is removed as a molten slag. The process was invented by F. Totzek at Heinrich Koppers, Essen, and further developed by Koppers Company in Louisiana, MO, under contract with the U.S. Bureau of Mines. The first commercial operation was at Oulu, Finland, in 1952 by 1979, 53 units had been built. Most of the plants are operated to produce a hydrogen-rich gas for use in ammonia synthesis. Developed by Lurgi. See also PRENFLO. 

In most processes the reaction takes place on an iron catalyst. The reaction pressure is normally in the range of 150 to 250 bar, and temperatures are in the range of 350°C to 550°C. At the usual commercial converter operating conditions, the conversion achieved per pass is only 20% to 30%53. In most commercial ammonia plants, the Haber recycle loop process is still used to give substantially complete conversion of the synthesis gas. In the Haber process the ammonia is separated from the recycle gas by cooling and condensation. Next the unconverted synthesis gas is supplemented with fresh makeup gas, and returned as feed to the ammonia synthesis converter74. 

In recent years several commercial plants have been constructed for conversion of coal to synthesis gas for chemical manufacturing. These include the Eastman Chemical s acetic anhydride plant, the Ube (Japan) ammonia plant, the SAR (Germany) oxo chemicals plant, and several coal to ammonia plants in China (e.g., Weihe, Huainan, and Lunan). The Ube plant and the SAR plant have since converted to lower-cost opportunity fuels (petroleum coke and residues). The Eastman plant is still operating exclusively on coal. Feedstock changes at the other plants illustrate the vulnerability of coal conversion processes to a changing economic climate. The fact that the Eastman process remains competitive under changing conditions is due to a set of special circumstances that favor a coal-based process. The success of the Eastman chemicals from coal complex demonstrates that synthesis gas from coal is a viable feedstock for some industrial chemicals under certain conditions. 

Commercial plants The first complete LAC plant, for 1,350-mtd ammonia, has been built for GSFC in India. Two other LAC plants, for 230-and 600-mtd ammonia, were commissioned in Australia. The latest LAC contract is under erection in China and produces hydrogen, ammonia and C02 under import of nitrogen from already existing facilities. There are extensive reference lists for Linde hydrogen and nitrogen plants and Ammonia Casale synthesis systems. 

Commercial plants More than 60 plants use the Tbpspe process concept. In addition, many plants based on other feedstocks use the Topspe ammonia synthesis technology. Since 1988, 52% of all new ammonia production capacity has been based on Tbpspe technology. 

In all commercial plants ammonia is recovered from the synthesis loop by cooling the synthesis gas to condense the ammonia under synthesis pressure. The liquid ammonia product is separated from the gas, which is recycled. Arrangement and location of the ammonia separator(s), recirculation compression, addition of makeup gas and extraction of purge gas are discussed in Section 4.5.1 (see also Figure 77). 

Urea is produced commercially by reacting NH3 and C02 at high pressure and temperature. The process is usually near an ammonia synthesis plant which produces both reactants. The two-step process is shown in Reactions 3.9 and 3.10 [5]. 

The Hikoshima plant started by importing technology for ammonia synthesis. A pilot plant having a daily production run of 5 tons was constructed utilizing the Claude process from France at a cost of 5,000,000 yen. The commercial process at Hikoshima started in 1924, but this system was new and needed many improvements. There were several accidents, causing explosions and casualties. Steady production was not reached until 1928. 

It was tested in several small 3 to 10 ton per day plants but was never operated intact on a large scale commercial basis. Instead the large commercial units became adaptations of the Haber process, the Cassale Process, or the Claude Process for ammonia synthesis. The American Process was originally described as using electrolytic hydrogen. This was much too expensive for commercial use in America at that time. Instead hydrogen was obtained from the reaction of steam with coal or later from the... 

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